Obstetric Anesthesia

Front 1

List major physiologic changes in pregnancy.

Back 1

1. Increased maternal blood volume/CO
2. Uterine enlargement
a) aortocaval compression
3. Decreased FRC
4. Increased minute volume
5. Decreased lower esophageal sphincter tone
6. Increased coagulation factors

Front 2

List hematologic changes.

Back 2

1. Plasma volume increased 40-50%
2. Total blood volume increased 25-40%
3. Red cell volume increased 20%
4. Fibrinogen increased 50%
5. Total plasma protein decreased to >6 g/dL

Front 3

List blood and plasma changes.

Back 3

1. Dilutional anemia
a) Hgb 10.5-11 g/dL
2. Increased clotting factors
a) VII, VIII, IX, and X
3. Increased fibrinogen
4. Increased risk of thromboembolism
5. Increase in WBC
6. Decreased CSF density
7. Increased GFR by 50-60%
8. Decreased plasma cholinesterase

Front 4

List cardiovascular changes.

Back 4

1. Decreased vascular resistance
2. Increased CO
a) 30-50%
3. Aortocaval compression
4. Supine hypotensive syndrome
5. Uterine displacement
6. Dysrhythmias
7. SV increased 30%
8. HR increased 15-20%
9. TPR decreased 15%
10. 3rd or 4th heart sound may be heard late pregnancy

Front 5

List not innocent cardiac changes.

Back 5

1. Systolic murmur >III
2. Any diastolic murmur
3. Severe arrhythmias
4. Unequivocal cardiac enlargement

Front 6

What effect can uterine position have on blood flow to the uterus?

Back 6

1. Flow can be decreased 40-50%
2. Hypotension can occur rapidly
3. Uteroplacental circulation is pressure dependent

Front 7

List ventilatory changes.

Back 7

1. Upper airway swelling
2. Use smaller ETT (6-7 mm) due to swollen false cords
3. Breast engorgement
4. Increased AP diameter
5. Diaphragm elevated 4 cm
6. Progesterone increases airway dilatation

Front 8

List respiratory changes.

Back 8

1. Tidal volume increased 45%
2. FRC decreased 20%
3. Inspiratory capacity increased 15%
4. Minute ventilation increased 45%
5. Alveolar ventilation increased 45%
6. No change in vital capacitance

Front 9

How do hormone changes affect respiratory status?

Back 9

Progesterone increases sensitivity to C02, which acts as a direct stimulant.

Front 10

List blood gas changes.

Back 10

1. Mild compensated metabolic alkalosis due to renal excretion of HC03
2. Right shift of oxyhemoglobin dissociation curve in the mother, left in the fetus.

Front 11

List GI changes.

Back 11

1. Displacement of stomach upward and leftward
2 Displacement of intrabdominal segment of esophagus into thorax
3. Decreased lower esophageal high pressure zone
4. Increased intragastric pressure
5. More acidic gastric secretions

Front 12

List altered drug responses.

Back 12

1. Decreased MAC
2. Faster induction from gases due to decreased FRC
3. Decreased LA requirements

Front 13

Where does blood to the fetus go through first?

Back 13

The liver

Front 14

What could happen as a result of excessive mechanical ventilation?

Back 14

Reduced maternal CO and uterine blood flow.

Front 15

How are oxygen, nutrients, and hormones delivered to the baby?

Back 15

Via the umbilical vein.

Front 16

How are wastes and carbon dioxide delivered away from the baby?

Back 16

Via the umbilical arteries.

Front 17

Explain fetal circulation in the placenta.

Back 17

1. Blood to placenta by 2 umbilical arteries
2. Capillaries to tips of fetal villi where exchange occurs
3. Returns to single umbilical vein

Front 18

List diffusion items.

Back 18

1. Oxygen
2. CO2
3. Fatty acids
4. Smaller ions
a) Sodium and Chloride
5. Glucose
a) via facilitate diffusion

Front 19

List active transport items.

Back 19

1. Amino acids
2. Water-soluble vitamins
3. Larger ions
a) calcium and iron

Front 20

What is bulk flow?

Back 20

Passage due to hydrostatic or osmotic gradient.
a) water

Front 21

List factors that cause decreased uterine blood flow.

Back 21

1. Uterine contractions
2. Hypertonus
3. Hypotension
4. Hypertension
5. Endogenous vasoconstriction
6. Exogenous vasoconstriction

Front 22

List things that could cause hypertonus.

Back 22

1. Abruptio placentae
2. Tetanic contraction
3. Overstimulation with oxytocin

Front 23

List things that could cause hypotension.

Back 23

1. Sympathetic block
2. Hypovolemic shock
3. Supine hypotensive syndrome

Front 24

List things causing endogenous vasoconstriction.

Back 24

1. Sympathetic discharge
2. Adrenal medullary activity

Front 25

List things causing exogenous vasoconstriction.

Back 25

1. Most sympathomimetics
a) mostly A-adrenergic
b) exception of ephedrine, which is a B-adrenergic

Front 26

List factors affecting oxygen transfer from mother to fetus.

Back 26

1. iIntravillous blood flow
2. Fetal-placental blood flow
3. Oxygen tension in maternal/fetal arterial blood
4. Oxygen affinity of maternal/fetal blood
5. Hgb concentration of maternal/fetal blood
6. Maternal/fetal blood pH and PCO2
7. Placental diffusing capacity
8. Placental oxygen consumption

Front 27

How can obstetric anesthesia affect uterine blood flow?

Back 27

1. Changing perfusion pressure.
2. Changing uterine vascular resistance
a) directly - changes in vascular tone
b) altering uterine contractions

Front 28

How should you adjust IV induction agents?

Back 28

1. Thiopental - decrease 20-40%
2. Propofol - at 2 mg/kg
3. Ketamine- at 0.25-1 mg/kg

Front 29

List factors concerning halogenated inhalation agents.

Back 29

1. Relaxing the uterus may increase blood flow
2. Give 1/2 MAC without problems
3. Best agent for uterine hyperstimulation or tetanic contraction
4. Relaxed uterus will increase bleeding

Front 30

What is the most prevalent complication of pregnancy?

Back 30

Hypertension.
7-10% of all pregnancies.

Front 31

What values constitute HTN from baseline obtained in the first timester?

Back 31

1. A rise in SBP of at least 30 mmHg
2. A rise in DBP of at least 15 mmHg
3. A rise in MAP of at least 20 mmHg

Front 32

What values constitute HTN when no baseline bp is available?

Back 32

1. SBP >= 140 mmHg
2. DBP >= 90 mmHg
3. MAP >= 105 mmHg

Obtain at least 2 measurements separated by at least 6 hours.

Front 33

List the 4 classifications of HTN.

Back 33

1. PIH
a) preeclmapsia/eclampsia
2. Chronic HTN preceding pregnancy
3. Chronic HTN with superimposed preeclampsia/eclampsia
4. Gestational HTN

Front 34

Define preeclampsia.

Back 34

The development of HTN with protenuria and/or generalized edema beyond the 20th week of gestation.

Front 35

How is preeclampsia classified?

Back 35

As mild or severe.

Front 36

What determines mild preeclampsia?

Back 36

1. BP of 140/90 or greater or increases by 30 mmHg (s) or 15 mmHg (d)
2. Proteinuria >300 mg/day or >1 gm/L in 2 random specimens

Front 37

What determines severe preeclampsia?

Back 37

1. BP of 160/110 or greater on 2 deparate occasions
2. Proteinuria - 5 gm/day and/or oliguria <400 ml

Front 38

What amount of edema is concerning?

Back 38

1. Generalized edema >1+ after 12 hours of bedrest
2. Weight gain >5 lbs/week

Front 39

List other factors or preeclampsia.

Back 39

1. Cerebral or visual distrubances
2. Pulmonary edema
3. Epigastric or RUQ pain
4. Impaired liver function
5. Thrombocytopenia

Front 40

Define chronic HTN preceding pregnancy.

Back 40

An elevated blood pressure of any etiology that manifests before the 20th week of pregnancy. Presents with the classic symptoms of preeclampsia.

Front 41

When does gestational HTN occur?

Back 41

In the second half of pregnancy or in the first 24 hours postpartum without evidence of preeclampsia.

Front 42

What is the etiology of preeclampsia?

Back 42

it is unknown.

Front 43

What prostaglandins appear to play a role in preeclampsia?

Back 43

1. Thromboxane A2
2. Prostacyclin

Front 44

What are the effects of thromboxane in preeclampsia?

Back 44

1. Levels are increased.

Front 45

List effects of thromboxane under normal circumstances.

Back 45

1. Increases vasoconstriction
2. Increases platelet aggregation
3. Increases uterine activity
4. Decreases uterine blood flow

Front 46

How are the levels of prostacyclin during preeclampsia?

Back 46

Levels are decreased.

Front 47

List effects of prostacyclin under normal circumstances.

Back 47

1. Decreases vasoconstriction
2. Decreases platelet aggregation
3. Decreases uterine activity
4. Increases uteroplacental bloodflow

Front 48

What does the preeclampsia triad consist of?

Back 48

1. HTN
2. Protenuria and/or
3. Generalized body edema

Front 49

When does preeclampsia occur?

Back 49

After the 20th week of gestation.

Front 50

When does preeclampsia resolve?

Back 50

Within 48 hours after delivery.

Front 51

What is preeclampsia called when it is complicated by seizures?

Back 51

Eclampsia

Front 52

How does HTN affect the CNS?

Back 52

CNS become hyperirritable due to cerebral edema from increased intracellular fluid volume in the brain cells. This can lead to grand mal seizures, coma, and/or cerebral hemorrhage.

Front 53

How does HTN affect peripheral vasculature?

Back 53

Exhibits extreme sensitivity to catecholamines, sympathomimetic drug, and oxytoxic agents.

Front 54

How does HTN affect cardiac vasculature?

Back 54

Generalized arterial vasoconstriction.

Front 55

How does HTN affect the workload of the heart?

Back 55

Increased afterload leads to LV failure and pulmonary edema.

Front 56

How does PIH affect the cardiovascular system?

Back 56

1. Increased blood viscosity
2. Decreased platelet counts
3. Increased FSP
4. Prolonged PTT
5. Left shift of the oxy-hgb dissociation curve

Front 57

What should you consider in giving fluids in PIH?

Back 57

1. Hypovolemia vs. hypernatremia
2. Fluid expansion vs. diuretics and vasodilaters.

Front 58

How does PIH affect the pulmonary system?

Back 58

1. VQ mismatch
2. Laryngeal edema
3. Normal PAP & PCWP unless there is pulmonary edema
4. Respiratory drive may be decreased with manesium.

Front 59

How does PIH affect the renal system?

Back 59

1. Decreased RBF
2. Decreased GFR
3. Decreased creatnine clearance
4. Decreased urea clearance
5. Proteinuria
6. Altered uric acid excretion
7. ARF/oliguria
8. Sodium retention

Front 60

Uric acid can be used to monitor severity of PIH. List levels and severity.

Back 60

1. Normal pregnant = 3.0-3.5 mg/dl
2. Mild PIH = >4.0 mg/dl
3. Severe PIH = >7.5 mg/dl

Front 61

How does PIH affect the liver?

Back 61

1. Subcapsular hepatic hemorrhage
2. RUQ pain
3. Jaundice
4. Ascites
5. Increased LFTs have no prognostic value
6. Rupture of hepatic capsule has 56-75% mortality

Front 62

How often does thrombocytopenia occur in women with preeclampsia?

Back 62

15-30%

Front 63

What are routine platelet counts in preeclamptic women?

Back 63

<100,000. Could be <10,000 in severe preeclampsia.

Front 64

What is the definitive treatment of PIH?

Back 64

Delivery of the fetus and placenta.

Front 65

List other treatments for PIH.

Back 65

1. Control of maternal HTN
a) diastolic <110 mmHg
2. Decrease cerebral irritibility
3. Improve circulation
4. Assure fetal viability
5. Correct coagulation abnormalities
6. Correct acid base and electrolyte abnormalities

Front 66

List predisposing factors for PIH.

Back 66

1. Primarily primiparous women (85%)
2. Chronic HTN
3. Renal disease
4. Insulin dependent diabetes
5. Obesity
6. Hx of preeclampsia
7. Hx of close relatives developing the disease
8. Condition associated with rapid uterine rupture
a) hydatiform moles, diabetes, multiple gestation

Front 67

What is the etiology of PIH?

Back 67

It is unknown.

Front 68

What are some theories of the cause of PIH?

Back 68

1. Hereditary
2. Immunologic Ag/Ab reaction
3. Prostacyclin/Thromboxane imbalance
4. Angiotensin II and PGE 2

Front 69

List pharmacologic treatments for PIH.

Back 69

1. Hydralizine
2. Diazoxide
3. Calcium channel blockers
4. Beta Blockers
5. Nitroglycerin
6. Nitroprusside
7. Diuretics

Front 70

What is the drug of choice in controlling preeclampsia and eclampsia?

Back 70

Magnesium sulfate

Front 71

Why is magnesium given?

Back 71

1. To prevent seizures
2. To lowers peripheral vascular resistance

Front 72

What is the mechanism of action of magnesium?

Back 72

1. Magnesium competes with calcium binding sites on the outside of the SR and prevents the increase in free intracellular calcium, which inhibits actin and myosin activity.
2. Mag decreases the release of acetylcholine at the NMJ and decreases sensitivity of the motor end plate to the action of acetylcholine.

Front 73

List effects of treatment with magnesium.

Back 73

1. Decreased cerebral irritability
2. Mild sedation
3. Mild vasodilation
4. Decreased uterine tone
5. Decreased uterine contractility
6. Prolonged action of NMB
7. Decreased ACH release
8. Decreased sensitivity to ACH release
9. Depressed muscle membrane excitability

Front 74

What is the therapeutic range of magnesium?

Back 74

4-5 mEq/L

Front 75

What is the normal plasma level of magnesium in pregnant women?

Back 75

1.5-2 mEq/L

Front 76

What effects will you see with mag levels of 5-10 mEq/L?

Back 76

1. Prolonged PQ interval
2. Widened QRS complex

Front 77

What effects will you see with mag levels of 10-12 mEq/L?

Back 77

1. Loss of deep tendon reflexes
2. Respiratory depression

Front 78

What effects will you see with mag levels of 15 mEq/L?

Back 78

1. SA and AV block
2. Respiratory paralysis

Front 79

What effects will you see with mag levels >25 mEq/L?

Back 79

Cardiac arrest

Front 80

How does mag affect the fetus?

Back 80

Mag crosses the placenta and causes neonatal hypotonia and respiratory depression.

Front 81

What is the dose of mag given?

Back 81

1. Bolus of 2-4 grams IV over 15-20 minutes followed by gtt at 1-4 grams/hr IV
2. 4 gram IM over 4 hours

Front 82

What considerations should you take in anesthetic management in pts on mag therapy?

Back 82

1. Mag potentiates both depolarizing and non-depolarizing NMBAs.
2. Monitor coag profile
3. Administer depressive agents cautiously.

Front 83

What should you keep in mind when administering NMBAs to a pt on mag therapy?

Back 83

1. Never administer a defisiculating dose
2. Standardize dose of succ to 1 mg/kg
3. Administer 1/2 to 1/3 maintenance dose of non-depolarizers

Front 84

What coags should you monitor on a pt on mag therapy

Back 84

1. PT/PTT
2. TEG
3. FSP
4. FDP

Front 85

List goals of anesthetic management of PIH.

Back 85

1. Oxygenate the mother and fetus
2. Avoid exacerbating compromised end organ function
3. Avoid further increases in CO
4. Avoid drugs excreted unchanged by kidney or that may accentuate liver dysfunction
5. Use CSE analgesia in early labor
a) load CLE slowly to avoid significant hypotension
6. Avoid agents the depress fetus and newborn
7. Avoid hypoxia and hypercarbia
8. Avoid free water
9. Avoid diuretics
10. Consider hypovolemia vs. hypernatremia
11. Consider pulmonary and cerebral edema vs. ARF

Front 86

List PIH anesthetic considerations.

Back 86

1. Thorough pre-op eval
2. Airway eval is crucial
3. Large bore IV
4. Aspiration prophylaxis before any anesthetic
5. Oxygen
6. Maximize uterine displacement
7. Evaluate coag profile
8. Labor epidural

Front 87

What should be considered with an epidural in a pt with PIH?

Back 87

1. Usually placed during active labor
2. Evaluate coag profile
3. Platelet count
4. Dose slowly
5. Preferred technique for C/S and SAB may drop BP and effect uteroplacental bloodflow

Front 88

List PIH considerations for general anesthesia.

Back 88

1. Indicated in fetal distress.
2. Take usual GA precautions
3. Expect small glottic opening and small, edematous and friable airway
4. Avoid ketamine
5. Reduce dose of muscle relaxant
6. Rapid sequence induction
7. Closely follow degree of paralysis
8. Extubate only when fully awake
9. Extubate only when full muscle strength returns

Front 89

Define eclampsia.

Back 89

Convulsion and/or coma not caused by coincidental neurological disease.

Front 90

When does eclampsia occur most of the time?

Back 90

During delivery (52%)

Front 91

List risk factors for eclampsia.

Back 91

1. Nulliparity
2. Multiple gestation
3. Molar pregnancy
4. Preexisting HTN
5. Renal disease
6. Previous hx of preeclampsia or eclampsia
7. Non-immune hydrops fetalis
8. Systemic lupus erythmatous

Front 92

List consideration for anesthetic management of the eclmaptic pt.

Back 92

1. Assessment of seizure control and neuro function
2. Maintenance of fluid balance
a) restrict fluid intake to 75-100 ml/hr
3. Blood pressure control
a) maintain diastolic bp at <100 mmHg
4. Continuous FHR monitoring
5. Lab investigations
a) PT/PTT, FDP, FSP, TED, platelet counts

Front 93

What is the method of choice in an eclamptic pt when no ICP is present?

Back 93

Epidural anesthesia

Front 94

When should epidural anesthesia be withheld in a pt with eclampsia?

Back 94

1. Suspected ICP
2. If pt exhibits evidence of a neuro deficit

Front 95

List characteristics of HELLP syndrome.

Back 95

1. Hemolysis
2. Elevated Liver enzymes
3. Low Platelet counts

Front 96

What is the hallmark sign of HELLP syndrome?

Back 96

Hemolysis

Front 97

When does HELLP usually present?

Back 97

Preterm

Front 98

List other signs and symptoms of HELLP syndrome.

Back 98

1. Malaise
2. Epigastric pain
3. N/V
4. Evidence of preeclampsia before delivery